The major objective of this research is to examine the interactions of leukocytes and platelets with endothelium in the microcirculation of the eye in several animal models in order to determine in what ways their local interactions contribute to an altered ocular vascular permeability. Experimental models include: the effects of intravitreal and systemic bacterial lipopolysaccharide (LPS); the inflammation induced by immune complexes, and the inflammation induced by specific chemotactic agents such as C5a. These studies are to be performed in rats and rabbits, and changes in the eye compared to those in skin. Leukocyte extravasation would be measured with 51 Chromium or 111 Indium labeled polymorphonuclear leukocytes and/or monocytes and correlated with altered vascular permeability as determined by 125 Iodine-albumin. This would be followed by similar studies in animals chemically or immunologically depleted of leukocytes, to determine the effect of this depletion on vascular permeability. Purified populations of PMNLs, monocytes, and lymphocytes would be infused in leukocyte depleted animals to determine whether alteration in vascular permeability could be restored. The role of platelets in these models would be investigated utilizing 111 Indium as label to determine deposition. The effect of leukocyte depletion on platelet deposition would also be examined. The role of circulating cells on the ocular inflammation induced by systemic LPS will be similarly evaluated in both rats and rabbits through both depletion and restoration studies using purified populations of inflammatory cells. In rabbits refractory to LPS (LPS "tolerant"), purified populations of circulating whole blood cells will be infused to determine whether any can restore the ocular response to systemic LPS. The consequence of intravascular complement-stimulated leukocyte aggregation will be studied in different vascular beds in the eye using Evan's blue dye and fluorescein-labeled dextrans. Histologic and electron microscopic examination will be a part of all these studies.